Backfire @ wot

[RS12Turbo]

So i'm trying to tune my engine via safc 2 after installing my custom header, evo3 16g, and Nismo fpr. Today after leaning out the hi throttle settings, and during a 3rd gear pull at wot, I got a backfire at around 3800-4000 rpm with boost at 14-15psi, and afr's were 12.6-12.8 What does a backfire mean?

[boost_boy]

So i'm trying to tune my engine via safc 2 after installing my custom header, evo3 16g, and Nismo fpr. Today after leaning out the hi throttle settings, and during a 3rd gear pull at wot, I got a backfire at around 3800-4000 rpm with boost at 14-15psi, and afr's were 12.6-12.8 What does a backfire mean?

Means you're getting ready to ruin your pistons. Your engine is telling you that it is lacking on fuel during your WOT session. Becareful when tuning. Start waaay rich and work your way back lean.

Dee

[RS12Turbo]

Means you're getting ready to ruin your pistons. Your engine is telling you that it is lacking on fuel during your WOT session. Becareful when tuning. Start waaay rich and work your way back lean.

Dee

Thats kinda what I thought it meant It wasn't doing this the other day...After "the other day"....I read on some DSM forum that the lo/hi Th- Points should be 69/70.....what they said made since, so I set mine to that. Apparently what works for dsm doesn't work on Nissans After I did that is when the backfire happened. No idea if setting the lo/hi th-points like that had anything to do with the backfire...but I went back and spread it out and set the lo to 30% and the hi to 60%. Took it for a spin and no more backfire. Kinda weird...but I dunno, it seems to be gone.I did some 4th gear pulls, and the afr's are staying around 12.2-12.5 from 3000-7000 rpms....and currently the Hi map settings are -20 from 3000 to 4500, then at 5000-7000 it's bumped up to -17, since the afr's climbed into the upper 13's when it was set to -20Is 12.2-12.5 a good range..or should it be lower than that?

[boost_boy]

Thats kinda what I thought it meant It wasn't doing this the other day...After "the other day"....I read on some DSM forum that the lo/hi Th- Points should be 69/70.....what they said made since, so I set mine to that. Apparently what works for dsm doesn't work on Nissans After I did that is when the backfire happened. No idea if setting the lo/hi th-points like that had anything to do with the backfire...but I went back and spread it out and set the lo to 30% and the hi to 60%. Took it for a spin and no more backfire. Kinda weird...but I dunno, it seems to be gone.I did some 4th gear pulls, and the afr's are staying around 12.2-12.5 from 3000-7000 rpms....and currently the Hi map settings are -20 from 3000 to 4500, then at 5000-7000 it's bumped up to -17, since the afr's climbed into the upper 13's when it was set to -20Is 12.2-12.5 a good range..or should it be lower than that?

I would set to at least -15 and see if your afr make it to the high 11s or a consistent 12 flat.

Dee

[Ca_Silvia]

I agree with Dee anything over 12 @ WOT is bad news

[RS12Turbo]

Ok...good to know. I will richen it up and see if I can get under 12....shouldn't be a prob.I'll let you guys know.....i'm out in Cali right now though, so it will be a week before I get back home to mess with it. Thanks again

[float_6969]

Over 12 isn't necessarily bad news, you just run a greater risk of detonation, especially on pump gas. I really don't like much more rich than 12:1, but it is safer.

If I were you, i would try to get them to stay between 11.7-12.3 at WOT. If you can get it to go from 11.9-12.1, that would be even better, but I don't think the SAFC has that kind of resolution.

[RS12Turbo]

Messed with it a little today...got the afr's to dip down into the 11's.....with the hi throttle set to -15. It kept cutting out at wot, with boost @ 15psi......not back firing, just cutting out. I'm wondering if it could be something else, like the spark blowing out, coil pack going out, etc.Didn't have this problem with the t25g.Any ideas? Should the spark plug gap be less than stock when using this turbo?

[float_6969]

You just took the thought right out of my head. I was going to suggest that you either have a coil going out or an ignitor failing. It could also simply be that the combustion pressures are simply too high for the stock ignition system to deal with at that spark plug gap.

If I were in your position I would reduce the gap on the plugs to about .9mm and see if that does anything for you. If it does improve, then you might contemplate some sort of modification to increase your spark intensity.

If it doesn't resolve the issue, I would start to examine your ignition components.

Also, what tune do you have on the ECU? Are you sure you aren't hitting some sort of programmed cutout?

[RS12Turbo]

Stock ecu........

Can you lessen the gap on ngk iridiums? Seems like it said on the box not to mess with the gap as the electrode might break or something...or I read it somewhere else. Maybe i'll throw in some coppers.

On the way home I turned the boost down from 16psi to 14psi, and adjusted the hi throttle to -18. For whatever reason turning it down to 14psi seemed to take care of it as it didn't cut out at all....and the afrs at wot in 4th were at a steady 12.0-12.1 from 3000 to 5000rpms. It's weird because once the rpms hit roughly 5500 rpms , boost spiked to 17-18, afrs climbed to 13.2, and it didn't cut out at all...just pulled like a sob So, not sure why it was cutting out earlier, or why it didn't cut out when boost spiked...maybe an intermittent thing or something. I'll still lessen the gap on the plugs and see what happens

[float_6969]

No, you can't change the gap on iridium's. You'll break the electrode.

I think you've exceeded the use of that SAFC man.

What your describing over 5K is the ECU retarding the timing based on the false information coming from the SAFC. The retarded timing is causing the turbo to spool up, and messing with your AFR's.

THIS IS A PERFECT EXAMPLE OF THE LIMITATIONS OF THE SAFC AND HOW IT CAN DAMAGE YOUR MOTOR!

That was for everyone not just you.

You NEED to get a chip for your injectors and MAFS. NOW! You are going to completely ruin that motor if you keep driving it like this.

Turn the boost down as low as it will go, and drive the car gingerly until you can get the ECU chipped.

I'm sorry to come across so strongly, but if you continue down this path you are going to grenade your motor. Plain and simple.

[RS12Turbo]

Greatly appreciated....thanks for the info sir

Yeah....i'll turn the boost down until I get a z32 maf, and chip.....but for now the safc will have to suffice

Can't boost creep happen other ways too....like when using a mbc? Also, I always heard boost creep is very common with dsm turbos.

On a side note....my Nismo fpr doesn't seem to be holding a steady setting. I had it set at 36psi at idle with the vac hose plugged in.... This morning I noticed it was at 42psi at idle. I've noticed this before...I'll adjust it, and a few days later, it's different. Does it have anything to do with changing the safc settings? I wouldn't think so
Modified by RS12Turbo at 11:50 AM 9/4/2009

[boost_boy]

Messed with it a little today...got the afr's to dip down into the 11's.....with the hi throttle set to -15. It kept cutting out at wot, with boost @ 15psi......not back firing, just cutting out. I'm wondering if it could be something else, like the spark blowing out, coil pack going out, etc.Didn't have this problem with the t25g.Any ideas? Should the spark plug gap be less than stock when using this turbo?

Though you've already mentioned it, another part of your probblem is too much boost. That turbo isn't worth more than 13 decent pounds of boost anyways, so keep it at or around 7-10psi and not much more. be sure your boost gauge is functioning properly because I've experience brand new autometer units telling lies and causing all kinds of confusing headaches.

Dee

[float_6969]

It's supposed to be 36 psi with the engine off and the fuel pump running.

I've never had a problem with mine changing. You need to make sure that you are comparing the pressure at the same manifold vacuum/boost.

[boost_boy]

Nismo regulators have been known to fail too. Nothing is a guarantee anymore, so be sure and check the components being mentioned because the advice on this thread seems to be in the ballpark of your issues.

Dee

[Buddyworm]

What your describing over 5K is the ECU retarding the timing based on the false information coming from the SAFC. The retarded timing is causing the turbo to spool up, and messing with your AFR's.

THIS IS A PERFECT EXAMPLE OF THE LIMITATIONS OF THE SAFC AND HOW IT CAN DAMAGE YOUR MOTOR!

The lean AFR's also might be the pulsewidth limiters in the ECU kicking in. But it'd be hard to tell without being able to fool around with them.

[slydn13]

i run 14psi with cheap ngk plugs never misses a beat. gaped t0 .76 from 1.1have also gapped many of iridiums / plantnuims without a problem.i would say do it just be carful

[dash]

Quote »That turbo isn't worth more than 13 decent pounds of boost anyways, so keep it at or around 7-10psi [/quote]perhaps u mean in the context of this particular std ecu/maf/SAFC setup.evo 16g is one of the best all around value/street performers... all the way up past 30psi proven on 4cyl monsters.

Boost creep is a well documented problem on 'em, especially with 3" exhaustsMost solved thru wastegate entry porting of the turbine housing. A manual boost controller will often get blamed for it.

To get around the limitations of the SAFC, you'll need the skill level of the advanced DSMers to go with it. The trick is to understand exactly what the unit is doing.... same way folks will "hack" a std afm onto a bigger pipe to run bigger injectors and so on

[float_6969]

The lean AFR's also might be the pulsewidth limiters in the ECU kicking in. But it'd be hard to tell without being able to fool around with them.

That doesn't explain his boost creep, unless the leaner AFR's are making his EGT's go up? That would do it too.

[RS12Turbo]

I put my ngk coppers back in, and lessened the gap to .20. Cutting out is gone completely. I removed my manual boost controller, and just screwed in the acuator arm a couple times to make it shorter. Boost is at 13-14psi, but the creep is still there once I hit 4500+ rpms. Got the afc adjusted.... the afrs are 11.5-11.8 throughout the rpm range now.Anyway to control creep? Would a ebc do the job...something like a AEM Tru Boost?

[float_6969]

No, creep is caused by a situation where there is more exhaust energy than the wastegate can bypass around the turbine. You only have a couple of options to fix the problem.

Reduce exhaust energy. If you are running too much timing retard, the excessive exhaust energy can cause the creep. This isn't something that you can rectify with your SAFC, and the SAFC may actually be CAUSING the problem. Get your ECU re-chipped for your mods.

Bigger wastegate. Not easy either since you're internally gated, but you can do a lot of things to increase the flow of energy through the wastegate. A dremel and a carbide bit will make quick work of the wastegate opening. Enlarge it a little bit. I have also seen someone modify the stock wastegate seal by using an exhaust valve head, machining it down and using it to make a larger head, so the wastegate could be made larger. Send the exhaust housing off to be extrude honed. Reduce the size of your exhaust. This will slow the flow of exhaust through the entire turbo and fix the creep as well.

Regardless, a boost controller can't fix creep.

[RS12Turbo]

Get your ECU re-chipped for your mods.

Dumb question, but any recommendations of a reputable company that sells chips? I've seen the Egay ones....how are they?

[Ca_Silvia]

Seriously do not do mail order chips. Call around to local tuners and see if they have ever done a CA before and go get it tuned on a dyno. Get something specific to you motor/mods etc.

[RS12Turbo]

You forget where I'm at......Dyno tuning isn't a problem......but finding a place that re-chips for a CA is next to impossible around here in Birmingham AL. God...I need to move back out to the west coast
Modified by RS12Turbo at 9:41 AM 9/11/2009

[float_6969]

I think the eBay chips are fine, but you'd better make sure they have a no DOA policy.

I know somebody on here was having problems with one and had to try like 3 different ones before he found one that worked.

[dash]

r u running stock 370s, stock afm ? what fuel pump ?Quote »...just pulled like a sob [/quote] this setup actually seems off to a good start and can only get better/safer as you get a better handle on tuning.I'd think the cutout at higher boost was the stock ecu cutout. I'd guess u could connect a digital voltmeter to AFM signal and verify the "trigger" voltage ?

nothing wrong with mail-order tunes in general. They r still big business. Why? ...because lots of folks have good experience with 'em.A few nico members here do CA chips... best1tuning I recall as one.Some here run ebay $50 chips fine also, and reportedly contacted the "tuner" on motor specifics, for a custom map to suit.I made a few notes when I see those sorta posts.... scattered about my pc

I can mail u some evoIII 16g wastegate porting pics that solved creep for DSMs, if u like

[RS12Turbo]

Just an update.....haven't driven it in a couple of weeks. I did however decided to quit being lazy and set the nismo fpr the proper way by using a jumper wire to run the fuel pump constant with the motor off. I knew it wasn't set properley but was very surprised that when I hooked up the jumper the gauge showed 48psi I backed the pressure down to 36psi as mentioned in the "how 2" thread. Haven't driven it yet...but any chances my cutting out could be from the excessive high fuel pressure?I may get it out tomorrow for a test drive and see what happens

[RS12Turbo]

Think I might of solved the cutting out issue.......I had posted a while back about how far away my maf should be from the turbo....since it was only 4 inches away. I moved it so it was about 8-10 inches away, and someone chimed in and said it should be further. Yesterday I put my CAI back on.....so that allowed me to place the maf further from the turbo.....it's about 15 inches or so from the turbo now, and which the pipe has a good curve to it. I cleaned the maf sensor too while I had it out. Took it for a drive, and it seem to rev better, acc is crisper..and best of all, it didn't cut out at 14psi at wot. I'll keep an eye on it..but I think that may of been it..knock on woodThere is still boost creep......i've been told by many it's because the wastegate needs to be ported and add a 35mm flapper. Other option i've been told is to snuff up the exhaust some, which I don't really want to do. I'll throw in the muffler butt plug and see if that helps control the creep some. If it does, maybe i'll just get a hi flow cat or resonator and go from there

[bradt]

Good deal. I think the stock ECU induces fuel cut at 15 to save the motor in the instance of a wastegate failure. The SAFC cannot bypass this IIRC.

If you are ever up in the Huntsville area, let me know. I would love to check out your car.

[RS12Turbo]

sure..sounds like a plan. There should be an organized meet up there again....last one i went to was a couple of years ago at a dyno shop there in huntsville. Pretty decent turnout.